Method for priority handling for buffer status reporting in a d2d communication system and device therefor

ABSTRACT

A method for transmitting, by a user equipment (UE), data in a wireless communication system, the method includes generating, at the UE, a medium access control (MAC) protocol data unit (PDU) containing at least one of a power headroom report (PHR) and a sidelink buffer status report (BSR); and transmitting, by the UE, the MAC PDU using uplink (UL) resources allocated to the UE, wherein the UE generates the MAC PDU, based on the UL resources and a predefined relative priority of a logical channel prioritization procedure, and wherein the predefined relative priority includes a following relative priority in decreasing order: MAC control element for PHR; and MAC control element for sidelink BSR.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation of co-pending U.S. patent applicationSer. No. 14/793,231 filed on Jul. 7, 2015, which claims the benefitunder 35 U.S.C. §119(e) to U.S. Provisional Application No. 62/054,362filed on Sep. 23, 2014, all of which are hereby expressly incorporatedby reference into the present application.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a wireless communication system and,more particularly, to a method for priority handling for buffer statusreporting in a D2D (Device to Device) communication system and a devicetherefor.

Discussion of the Related Art

As an example of a mobile communication system to which the presentinvention is applicable, a 3rd Generation Partnership Project Long TermEvolution (hereinafter, referred to as LTE) communication system isdescribed in brief

FIG. 1 is a view schematically illustrating a network structure of anE-UMTS as an exemplary radio communication system. An Evolved UniversalMobile Telecommunications System (E-UMTS) is an advanced version of aconventional Universal Mobile Telecommunications System (UMTS) and basicstandardization thereof is currently underway in the 3GPP. E-UMTS may begenerally referred to as a Long Term Evolution (LTE) system. For detailsof the technical specifications of the UMTS and E-UMTS, reference can bemade to Release 7 and Release 8 of “3rd Generation Partnership Project;Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), eNode Bs(eNBs), and an Access Gateway (AG) which is located at an end of thenetwork (E-UTRAN) and connected to an external network. The eNBs maysimultaneously transmit multiple data streams for a broadcast service, amulticast service, and/or a unicast service.

One or more cells may exist per eNB. The cell is set to operate in oneof bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides adownlink (DL) or uplink (UL) transmission service to a plurality of UEsin the bandwidth. Different cells may be set to provide differentbandwidths. The eNB controls data transmission or reception to and froma plurality of UEs. The eNB transmits DL scheduling information of DLdata to a corresponding UE so as to inform the UE of a time/frequencydomain in which the DL data is supposed to be transmitted, coding, adata size, and hybrid automatic repeat and request (HARQ)-relatedinformation. In addition, the eNB transmits UL scheduling information ofUL data to a corresponding UE so as to inform the UE of a time/frequencydomain which may be used by the UE, coding, a data size, andHARQ-related information. An interface for transmitting user traffic orcontrol traffic may be used between eNBs. A core network (CN) mayinclude the AG and a network node or the like for user registration ofUEs. The AG manages the mobility of a UE on a tracking area (TA) basis.One TA includes a plurality of cells.

Device to device (D2D) communication refers to the distributedcommunication technology that directly transfers traffic betweenadjacent nodes without using infrastructure such as a base station. In aD2D communication environment, each node such as a portable terminaldiscovers user equipment physically adjacent thereto and transmitstraffic after setting communication session. In this way, since D2Dcommunication may solve traffic overload by distributing trafficconcentrated into the base station, the D2D communication may havereceived attention as the element technology of the next generationmobile communication technology after 4G. For this reason, the standardinstitute such as 3GPP or IEEE has proceeded to establish the D2Dcommunication standard on the basis of LTE-A or Wi-Fi, and Qualcomm hasdeveloped their own D2D communication technology.

It is expected that the D2D communication contributes to increasethroughput of a mobile communication system and create new communicationservices. Also, the D2D communication may support proximity based socialnetwork services or network game services. The problem of link of a userequipment located at a shade zone may be solved by using a D2D link as arelay. In this way, it is expected that the D2D technology will providenew services in various fields.

The D2D communication technologies such as infrared communication,ZigBee, radio frequency identification (RFID) and near fieldcommunications (NFC) based on the RFID have been already used. However,since these technologies support communication only of a specific objectwithin a limited distance (about 1 m), it is difficult for thetechnologies to be regarded as the D2D communication technologiesstrictly.

Although the D2D communication has been described as above, details of amethod for transmitting data from a plurality of D2D user equipmentswith the same resource have not been suggested.

SUMMARY OF THE INVENTION

The object of the present invention can be achieved by providing amethod for operating by an apparatus in wireless communication system,the method comprising; generating a MAC PDU (Medium Access ControlProtocol Data Unit) if both of a PHR (Power Headroom Reporting) and asidelink BSR (Buffer Status Reporting) are generated while the UEcommunicates with other UEs directly using a sidelink; and transmittingthe MAC PDU, wherein the PHR is prioritized over the sidelink BSR whenthe UE prioritizes between the PHR and the sidelink BSR in the generatedMAC PDU.

In another aspect of the present invention provided herein is anapparatus in the wireless communication system, the apparatuscomprising: an RF (radio frequency) module; and a processor configuredto control the RF module, wherein the processor is configured togenerate a MAC PDU (Medium Access Control Protocol Data Unit) if both ofa PHR (Power Headroom Reporting) and a sidelink BSR (Buffer StatusReporting) are generated while the UE communicates with other UEsdirectly using a sidelink, and to transmit the MAC PDU, wherein the PHRis prioritized over the sidelink BSR when the UE prioritizes between thePHR and the sidelink BSR in the generated MAC PDU.

Preferably, the method further comprising: after the UE allocates anuplink resource to a PHR MAC CE (Control Element) and a correspondingMAC sub-header in the MAC PDU, checking whether a remaining uplinkresource in the MAC PDU can accommodate a sidelink BSR MAC CE and acorresponding MAC sub-header; if the remaining uplink resource canaccommodate the sidelink BSR MAC CE and the corresponding MACsub-header, allocating an uplink resource to the sidelink BSR MAC CE andthe corresponding MAC sub-header.

Preferably, the method further comprising: after the UE allocates theuplink resource to the sidelink BSR MAC CE and the corresponding MACsub-header in the MAC PDU, allocating a remaining uplink resource in MACPDU to uplink data except data from UL-CCCH (Uplink-Common ControlChannel), or padding BSR.

Preferably, the PHR is related to scheduling assistant information foruplink data transmission via Uu interface.

Preferably, the PHR is transmitted using a PHR MAC CE, an extended PHRMAC CE, or a dual connectivity PHR MAC CE.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 is a diagram showing a network structure of an Evolved UniversalMobile Telecommunications System (E-UMTS) as an example of a wirelesscommunication system;

FIG. 2A is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS), and FIG. 2B is ablock diagram depicting architecture of a typical E-UTRAN and a typicalEPC;

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3rd generationpartnership project (3GPP) radio access network standard;

FIG. 4 is a diagram of an example physical channel structure used in anE-UMTS system;

FIG. 5 is a block diagram of a communication apparatus according to anembodiment of the present invention

FIG. 6 is a diagram for prioritization of two logical channels for threedifferent uplink grants;

FIG. 7 is a diagram for signaling of buffer status and power-headroomreports;

FIG. 8A is a diagram for a Short BSR and Truncated BSR MAC controlelement, FIG. 8B is for a Long BSR MAC control element;

FIG. 9 is an example of default data path for a normal communication;

FIGS. 10 and 11 are examples of data path scenarios for a proximitycommunication;

FIG. 12 is a conceptual diagram illustrating for a non-roaming referencearchitecture;

FIG. 13A is a conceptual diagram illustrating for User-Plane protocolstack for ProSe Direct Communication, and FIG. 13B is Control-Planeprotocol stack for ProSe Direct Communication;

FIG. 14 is a conceptual diagram illustrating for a PC5 interface fordevice to device direct discovery;

FIG. 15 is a conceptual diagram for priority handling buffer statusreporting according to embodiments of the present invention; and

FIG. 16 is an example for priority handling buffer status reportingaccording to embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Universal mobile telecommunications system (UMTS) is a 3rd Generation(3G) asynchronous mobile communication system operating in wideband codedivision multiple access (WCDMA) based on European systems, globalsystem for mobile communications (GSM) and general packet radio services(GPRS). The long-term evolution (LTE) of UMTS is under discussion by the3rd generation partnership project (3GPP) that standardized UMTS.

The 3GPP LTE is a technology for enabling high-speed packetcommunications. Many schemes have been proposed for the LTE objectiveincluding those that aim to reduce user and provider costs, improveservice quality, and expand and improve coverage and system capacity.The 3G LTE requires reduced cost per bit, increased serviceavailability, flexible use of a frequency band, a simple structure, anopen interface, and adequate power consumption of a terminal as anupper-level requirement.

Hereinafter, structures, operations, and other features of the presentinvention will be readily understood from the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Embodiments described later are examples in which technicalfeatures of the present invention are applied to a 3GPP system.

Although the embodiments of the present invention are described using along term evolution (LTE) system and a LTE-advanced (LTE-A) system inthe present specification, they are purely exemplary. Therefore, theembodiments of the present invention are applicable to any othercommunication system corresponding to the above definition. In addition,although the embodiments of the present invention are described based ona frequency division duplex (FDD) scheme in the present specification,the embodiments of the present invention may be easily modified andapplied to a half-duplex FDD (H-FDD) scheme or a time division duplex(TDD) scheme.

FIG. 2A is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS). The E-UMTS may bealso referred to as an LTE system. The communication network is widelydeployed to provide a variety of communication services such as voice(VoIP) through IMS and packet data.

As illustrated in FIG. 2A, the E-UMTS network includes an evolved UMTSterrestrial radio access network (E-UTRAN), an Evolved Packet Core (EPC)and one or more user equipment. The E-UTRAN may include one or moreevolved NodeB (eNodeB) 20, and a plurality of user equipment (UE) 10 maybe located in one cell. One or more E-UTRAN mobility management entity(MME)/system architecture evolution (SAE) gateways 30 may be positionedat the end of the network and connected to an external network.

As used herein, “downlink” refers to communication from eNodeB 20 to UE10, and “uplink” refers to communication from the UE to an eNodeB. UE 10refers to communication equipment carried by a user and may be alsoreferred to as a mobile station (MS), a user terminal (UT), a subscriberstation (SS) or a wireless device.

FIG. 2B is a block diagram depicting architecture of a typical E-UTRANand a typical EPC.

As illustrated in FIG. 2B, an eNodeB 20 provides end points of a userplane and a control plane to the UE 10. MME/SAE gateway 30 provides anend point of a session and mobility management function for UE 10. TheeNodeB and MME/SAE gateway may be connected via an Si interface.

The eNodeB 20 is generally a fixed station that communicates with a UE10, and may also be referred to as a base station (BS) or an accesspoint. One eNodeB 20 may be deployed per cell. An interface fortransmitting user traffic or control traffic may be used between eNodeBs20.

The MME provides various functions including NAS signaling to eNodeBs20, NAS signaling security, AS Security control, Inter CN node signalingfor mobility between 3GPP access networks, Idle mode UE Reachability(including control and execution of paging retransmission), TrackingArea list management (for UE in idle and active mode), PDN GW andServing GW selection, MME selection for handovers with MME change, SGSNselection for handovers to 2G or 3G 3GPP access networks, Roaming,Authentication, Bearer management functions including dedicated bearerestablishment, Support for PWS (which includes ETWS and CMAS) messagetransmission. The SAE gateway host provides assorted functions includingPer-user based packet filtering (by e.g. deep packet inspection), LawfulInterception, UE IP address allocation, Transport level packet markingin the downlink, UL and DL service level charging, gating and rateenforcement, DL rate enforcement based on APN-AMBR. For clarity MME/SAEgateway 30 will be referred to herein simply as a “gateway,” but it isunderstood that this entity includes both an MME and an SAE gateway.

A plurality of nodes may be connected between eNodeB 20 and gateway 30via the Si interface. The eNodeBs 20 may be connected to each other viaan X2 interface and neighboring eNodeBs may have a meshed networkstructure that has the X2 interface.

As illustrated, eNodeB 20 may perform functions of selection for gateway30, routing toward the gateway during a Radio Resource Control (RRC)activation, scheduling and transmitting of paging messages, schedulingand transmitting of Broadcast Channel (BCCH) information, dynamicallocation of resources to UEs 10 in both uplink and downlink,configuration and provisioning of eNodeB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE ACTIVE state. In the EPC, and as noted above, gateway 30 mayperform functions of paging origination, LTE-IDLE state management,ciphering of the user plane, System Architecture Evolution (SAE) bearercontrol, and ciphering and integrity protection of Non-Access Stratum(NAS) signaling.

The EPC includes a mobility management entity (MME), a serving-gateway(S-GW), and a packet data network-gateway (PDN-GW). The MME hasinformation about connections and capabilities of UEs, mainly for use inmanaging the mobility of the UEs. The S-GW is a gateway having theE-UTRAN as an end point, and the PDN-GW is a gateway having a packetdata network (PDN) as an end point.

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3GPP radioaccess network standard. The control plane refers to a path used fortransmitting control messages used for managing a call between the UEand the E-UTRAN. The user plane refers to a path used for transmittingdata generated in an application layer, e.g., voice data or Internetpacket data.

A physical (PHY) layer of a first layer provides an information transferservice to a higher layer using a physical channel. The PHY layer isconnected to a medium access control (MAC) layer located on the higherlayer via a transport channel. Data is transported between the MAC layerand the PHY layer via the transport channel. Data is transported betweena physical layer of a transmitting side and a physical layer of areceiving side via physical channels. The physical channels use time andfrequency as radio resources. In detail, the physical channel ismodulated using an orthogonal frequency division multiple access (OFDMA)scheme in downlink and is modulated using a single carrier frequencydivision multiple access (SC-FDMA) scheme in uplink.

The MAC layer of a second layer provides a service to a radio linkcontrol (RLC) layer of a higher layer via a logical channel. The RLClayer of the second layer supports reliable data transmission. Afunction of the RLC layer may be implemented by a functional block ofthe MAC layer. A packet data convergence protocol (PDCP) layer of thesecond layer performs a header compression function to reduceunnecessary control information for efficient transmission of anInternet protocol (IP) packet such as an IP version 4 (IPv4) packet oran IP version 6 (IPv6) packet in a radio interface having a relativelysmall bandwidth.

A radio resource control (RRC) layer located at the bottom of a thirdlayer is defined only in the control plane. The RRC layer controlslogical channels, transport channels, and physical channels in relationto configuration, re-configuration, and release of radio bearers (RBs).An RB refers to a service that the second layer provides for datatransmission between the UE and the E-UTRAN. To this end, the RRC layerof the UE and the RRC layer of the E-UTRAN exchange RRC messages witheach other.

One cell of the eNB is set to operate in one of bandwidths such as 1.25,2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplinktransmission service to a plurality of UEs in the bandwidth. Differentcells may be set to provide different bandwidths.

Downlink transport channels for transmission of data from the E-UTRAN tothe UE include a broadcast channel (BCH) for transmission of systeminformation, a paging channel (PCH) for transmission of paging messages,and a downlink shared channel (SCH) for transmission of user traffic orcontrol messages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted through the downlink SCH and mayalso be transmitted through a separate downlink multicast channel (MCH).

Uplink transport channels for transmission of data from the UE to theE-UTRAN include a random access channel (RACH) for transmission ofinitial control messages and an uplink SCH for transmission of usertraffic or control messages. Logical channels that are defined above thetransport channels and mapped to the transport channels include abroadcast control channel (BCCH), a paging control channel (PCCH), acommon control channel (CCCH), a multicast control channel (MCCH), and amulticast traffic channel (MTCH).

FIG. 4 is a view showing an example of a physical channel structure usedin an E-UMTS system. A physical channel includes several subframes on atime axis and several subcarriers on a frequency axis. Here, onesubframe includes a plurality of symbols on the time axis. One subframeincludes a plurality of resource blocks and one resource block includesa plurality of symbols and a plurality of subcarriers. In addition, eachsubframe may use certain subcarriers of certain symbols (e.g., a firstsymbol) of a subframe for a physical downlink control channel (PDCCH),that is, an L1/L2 control channel. In FIG. 4, an L1/L2 controlinformation transmission area (PDCCH) and a data area (PDSCH) are shown.In one embodiment, a radio frame of 10 ms is used and one radio frameincludes 10 subframes. In addition, one subframe includes twoconsecutive slots. The length of one slot may be 0.5 ms. In addition,one subframe includes a plurality of OFDM symbols and a portion (e.g., afirst symbol) of the plurality of OFDM symbols may be used fortransmitting the L1/L2 control information. A transmission time interval(TTI) which is a unit time for transmitting data is 1 ms.

A base station and a UE mostly transmit/receive data via a PDSCH, whichis a physical channel, using a DL-SCH which is a transmission channel,except a certain control signal or certain service data. Informationindicating to which UE (one or a plurality of UEs) PDSCH data istransmitted and how the UE receive and decode PDSCH data is transmittedin a state of being included in the PDCCH.

For example, in one embodiment, a certain PDCCH is CRC-masked with aradio network temporary identity (RNTI) “A” and information about datais transmitted using a radio resource “B” (e.g., a frequency location)and transmission format information “C” (e.g., a transmission blocksize, modulation, coding information or the like) via a certainsubframe. Then, one or more UEs located in a cell monitor the PDCCHusing its RNTI information. And, a specific UE with RNTI “A” reads thePDCCH and then receive the PDSCH indicated by B and C in the PDCCHinformation.

FIG. 5 is a block diagram of a communication apparatus according to anembodiment of the present invention.

The apparatus shown in FIG. 5 can be a user equipment (UE) and/or eNBadapted to perform the above mechanism, but it can be any apparatus forperforming the same operation.

As shown in FIG. 5, the apparatus may comprises a DSP/microprocessor(110) and RF module (transceiver; 135). The DSP/microprocessor (110) iselectrically connected with the transceiver (135) and controls it. Theapparatus may further include power management module (105), battery(155), display (115), keypad (120), SIM card (125), memory device (130),speaker (145) and input device (150), based on its implementation anddesigner's choice.

Specifically, FIG. 5 may represent a UE comprising a receiver (135)configured to receive a request message from a network, and atransmitter (135) configured to transmit the transmission or receptiontiming information to the network. These receiver and the transmittercan constitute the transceiver (135). The UE further comprises aprocessor (110) connected to the transceiver (135: receiver andtransmitter).

Also, FIG. 5 may represent a network apparatus comprising a transmitter(135) configured to transmit a request message to a UE and a receiver(135) configured to receive the transmission or reception timinginformation from the UE. These transmitter and receiver may constitutethe transceiver (135). The network further comprises a processor (110)connected to the transmitter and the receiver. This processor (110) maybe configured to calculate latency based on the transmission orreception timing information.

FIG. 6 is a diagram for prioritization of two logical channels for threedifferent uplink grants.

Multiple logical channels of different priorities can be multiplexedinto the same transport block using the same MAC multiplexingfunctionality as in the downlink. However, unlike the downlink case,where the prioritization is under control of the scheduler and up to theimplementation, the uplink multiplexing is done according to a set ofwell-defined rules in the terminal as a scheduling grant applies to aspecific uplink carrier of a terminal, not to a specific radio bearerwithin the terminal. Using radio-bearer-specific scheduling grants wouldincrease the control signaling overhead in the downlink and henceper-terminal scheduling is used in LTE.

The simplest multiplexing rule would be to serve logical channels instrict priority order. However, this may result in starvation oflower-priority channels; all resources would be given to thehigh-priority channel until its transmission buffer is empty. Typically,an operator would instead like to provide at least some throughput forlow-priority services as well. Therefore, for each logical channel in anLTE terminal, a prioritized data rate is configured in addition to thepriority value. The logical channels are then served in decreasingpriority order up to their prioritized data rate, which avoidsstarvation as long as the scheduled data rate is at least as large asthe sum of the prioritized data rates. Beyond the prioritized datarates, channels are served in strict priority order until the grant isfully exploited or the buffer is empty. This is illustrated in FIG. 6.

Regarding FIG. 6, it may be assumed that a priority of the logicalchannel 1 (LCH 1) is higher than a priority of the logical channel 2(LCH 2). In case of (A), all prioritized data of the LCH 1 can betransmitted and a portion of prioritized data of the LCH 2 can betransmitted until amount of the scheduled data rate. In case of (B), allprioritized data of the LCH 1 and all prioritized data of the LCH 2 canbe transmitted. In case of (C) all prioritized data of the LCH 1 and allprioritized data of the LCH 2 can be transmitted and a portion of dataof the LCH 1 can be further transmitted.

FIG. 7 is a diagram for signaling of buffer status and power-headroomreports.

The scheduler needs knowledge about the amount of data awaitingtransmission from the terminals to assign the proper amount of uplinkresources. Obviously, there is no need to provide uplink resources to aterminal with no data to transmit as this would only result in theterminal performing padding to fill up the granted resources. Hence, asa minimum, the scheduler needs to know whether the terminal has data totransmit and should be given a grant. This is known as a schedulingrequest.

The use of a single bit for the scheduling request is motivated by thedesire to keep the uplink overhead small, as a multi-bit schedulingrequest would come at a higher cost. A consequence of the single bitscheduling request is the limited knowledge at the eNodeB about thebuffer situation at the terminal when receiving such a request.Different scheduler implementations handle this differently. Onepossibility is to assign a small amount of resources to ensure that theterminal can exploit them efficiently without becoming power limited.Once the terminal has started to transmit on the UL-SCH, more detailedinformation about the buffer status and power headroom can be providedthrough the inband MAC control message, as discussed below.

Terminals that already have a valid grant obviously do not need torequest uplink resources. However, to allow the scheduler to determinethe amount of resources to grant to each terminal in future subframes,information about the buffer situation and the power availability isuseful, as discussed above. This information is provided to thescheduler as part of the uplink transmission through MAC controlelement. The LCID field in one of the MAC subheaders is set to areserved value indicating the presence of a buffer status report, asillustrated in FIG. 7.

From a scheduling perspective, buffer information for each logicalchannel is beneficial, although this could result in a significantoverhead. Logical channels are therefore grouped into logical-channelgroups and the reporting is done per group. The buffer-size field in abuffer-status report indicates the amount of data awaiting transmissionacross all logical channels in a logical-channel group. A buffer statusreport represents one or all four logical-channel groups and can betriggered for the following reasons:

i) Arrival of data with higher priority than currently in thetransmission buffer—that is, data in a logical-channel group with higherpriority than the one currently being transmitted—as this may impact thescheduling decision.

ii) Change of serving cell, in which case a buffer-status report isuseful to provide the new serving cell with information about thesituation in the terminal.

iii) Periodically as controlled by a timer.

iv) Instead of padding. If the amount of padding required to match thescheduled transport block size is larger than a buffer-status report, abuffer-status report is inserted. Clearly it is better to exploit theavailable payload for useful scheduling information instead of paddingif possible.

The Buffer Status Reporting (BSR) procedure is used to provide a servingeNB with information about the amount of data available for transmission(DAT) in the UL buffers of the UE. RRC may control BSR reporting byconfiguring the two timers periodicBSR-Timer and retxBSR-Timer and by,for each logical channel, optionally signaling Logical Channel Groupwhich allocates the logical channel to an LCG (Logical Channel Group).

For the Buffer Status reporting procedure, the UE may consider all radiobearers which are not suspended and may consider radio bearers which aresuspended. A Buffer Status Report (BSR) may be triggered if any of thefollowing events occur:

-   -   UL data, for a logical channel which belongs to a LCG, becomes        available for transmission in the RLC entity or in the PDCP        entity and either the data belongs to a logical channel with        higher priority than the priorities of the logical channels        which belong to any LCG and for which data is already available        for transmission, or there is no data available for transmission        for any of the logical channels which belong to a LCG, in which        case the BSR is referred below to as “Regular BSR”;    -   UL resources are allocated and number of padding bits is equal        to or larger than the size of the Buffer Status Report MAC        control element plus its subheader, in which case the BSR is        referred below to as “Padding BSR”;    -   retxBSR-Timer expires and the UE has data available for        transmission for any of the logical channels which belong to a        LCG, in which case the BSR is referred below to as “Regular        BSR”;    -   periodicBSR-Timer expires, in which case the BSR is referred        below to as “Periodic BSR”.

For Regular and Periodic BSR, if more than one LCG has data availablefor transmission in the TTI where the BSR is transmitted, the UE mayreport Long BSR. If else, the UE may report Short BSR.

If the Buffer Status reporting procedure determines that at least oneBSR has been triggered and not cancelled, if the UE has UL resourcesallocated for new transmission for this TTI, the UE may instruct theMultiplexing and Assembly procedure to generate the BSR MAC controlelement(s), start or restart periodicBSR-Timer except when all thegenerated BSRs are Truncated BSRs, and start or restart retxBSR-Timer.

A MAC PDU may contain at most one MAC BSR control element, even whenmultiple events trigger a BSR by the time a BSR can be transmitted inwhich case the Regular BSR and the Periodic BSR shall have precedenceover the padding BSR.

The UE may restart retxBSR-Timer upon indication of a grant fortransmission of new data on any UL-SCH.

All triggered BSRs may be cancelled in case UL grants in this subframecan accommodate all pending data available for transmission but is notsufficient to additionally accommodate the BSR MAC control element plusits subheader. All triggered BSRs shall be cancelled when a BSR isincluded in a MAC PDU for transmission.

The UE shall transmit at most one Regular/Periodic BSR in a TTI. If theUE is requested to transmit multiple MAC PDUs in a TTI, it may include apadding BSR in any of the MAC PDUs which do not contain aRegular/Periodic BSR.

All BSRs transmitted in a TTI always reflect the buffer status after allMAC PDUs have been built for this TTI. Each LCG shall report at the mostone buffer status value per TTI and this value shall be reported in allBSRs reporting buffer status for this LCG.

In summary, the BSR is triggered in any of the following situation:

i) when data arrive for a logical channel which has higher priority thanthe logical channels whose buffers are not empty;

ii) when data become available for the UE's buffer, which is empty;

iii) when the retxBSR-Timer expires and there is still data in the UE'sbuffer;

iv) when a periodicBSR-Timer expires; or

v) when the remaining space in a MAC PDU can accommodate a BSR.

FIG. 8A is a diagram for a Short BSR and Truncated BSR MAC controlelement, FIG. 8B is for a Long BSR MAC control element.

Buffer Status Report (BSR) MAC control elements consist of either: i)Short BSR and Truncated BSR format: one LCG ID field and onecorresponding Buffer Size field or ii) Long BSR format: four Buffer Sizefields, corresponding to LCG IDs #0 through #3.

The BSR formats are identified by MAC PDU subheaders with LCIDs asspecified in Table 1.

TABLE 1 Index LCID values 00000 CCCH 00001-01010 Identity of the logicalchannel 01011-10110 Reserved 10111 ProSe Truncated BSR 11000 ProSe BSR11001 Extended Power Headroom Report 11010 Power Headroom Report 11011C-RNTI 11100 Truncated BSR 11101 Short BSR 11110 Long BSR 11111 Padding

The fields LCG ID and Buffer Size are defined as follow:

-   -   LCG ID: The Logical Channel Group ID field identifies the group        of logical channel(s) which buffer status is being reported. The        length of the field is 2 bits;    -   Buffer Size: The Buffer Size field identifies the total amount        of data available across all logical channels of a logical        channel group after all MAC PDUs for the TTI have been built.        The amount of data is indicated in number of bytes. It shall        include all data that is available for transmission in the RLC        layer and in the PDCP layer; the definition of what data shall        be considered as available for transmission. The size of the RLC        and MAC headers are not considered in the buffer size        computation. The length of this field is 6 bits. If        extendedBSR-Sizes is not configured, the values taken by the        Buffer Size field are shown in Table 2. If extendedBSR-Sizes is        configured, the values taken by the Buffer Size field are shown        in Table 3.

TABLE 2 Buffer Size Index (BS) value [bytes]  0 BS = 0  1    0 < BS <=10  2   10 < BS <= 12  3   12 < BS <= 14  4   14 < BS <= 17  5   17 < BS<= 19  6   19 < BS <= 22  7   22 < BS <= 26  8   26 < BS <= 31  9   31 <BS <= 36 10   36 < BS <= 42 11   42 < BS <= 49 12   49 < BS <= 57 13  57 < BS <= 67 14   67 < BS <= 78 15   78 < BS <= 91 16   91 < BS <=107 17   107 < BS <= 125 18   125 < BS <= 146 19   146 < BS <= 171 20  171 < BS <= 200 21   200 < BS <= 234 22   234 < BS <= 274 23   274 <BS <= 321 24   321 < BS <= 376 25   376 < BS <= 440 26   440 < BS <= 51527   515 < BS <= 603 28   603 < BS <= 706 29   706 < BS <= 826 30   826< BS <= 967 31   967 < BS <= 1132 32  1132 < BS <= 1326 33  1326 < BS <=1552 34  1552 < BS <= 1817 35  1817 < BS <= 2127 36  2127 < BS <= 249037  2490 < BS <= 2915 38  2915 < BS <= 3413 39  3413 < BS <= 3995 40 3995 < BS <= 4677 41  4677 < BS <= 5476 42  5476 < BS <= 6411 43  6411< BS <= 7505 44  7505 < BS <= 8787 45  8787 < BS <= 10287 46  10287 < BS<= 12043 47  12043 < BS <= 14099 48  14099 < BS <= 16507 49  16507 < BS<= 19325 50  19325 < BS <= 22624 51  22624 < BS <= 26487 52  26487 < BS<= 31009 53  31009 < BS <= 36304 54  36304 < BS <= 42502 55  42502 < BS<= 49759 56  49759 < BS <= 58255 57  58255 < BS <= 68201 58  68201 < BS<= 79846 59  79846 < BS <= 93479 60  93479 < BS <= 109439 61 109439 < BS<= 128125 62 128125 < BS <= 150000 63 BS > 150000

TABLE 3  0 BS = 0  1    0 < BS <= 10  2    10 < BS <= 13  3    13 < BS<= 16  4    16 < BS <= 19  5    19 < BS <= 23  6    23 < BS <= 29  7   29 < BS <= 35  8    35 < BS <= 43  9    43 < BS <= 53 10    53 < BS<= 65 11    65 < BS <= 80 19    80 < BS <= 98 13    98 < BS <= 120 14  120 < BS <= 147 15   147 < BS <= 181 16   181 < BS <= 223 17   223 <BS <= 274 18   274 < BS <= 337 19   337 < BS <= 414 20   414 < BS <= 50921   509 < BS <= 625 22   625 < BS <= 769 23   769 < BS <= 945 24   945< BS <= 1162 25   1162 < BS <= 1429 26   1429 < BS <= 1757 27   1757 <BS <= 2161 28   2161 < BS <= 2657 29   2657 < BS <= 3267 30   3267 < BS<= 4017 31   4017 < BS <= 4940 32   4940 < BS <= 6074 33   6074 < BS <=7469 34   7469 < BS <= 9185 35   9185 < BS <= 11294 36  11294 < BS <=13888 37  13888 < BS <= 17077 38  17077 < BS <= 20999 39  20999 < BS <=25822 40  25822 < BS <= 31752 41  31752 < BS <= 39045 42  39045 < BS <=48012 43  48012 < BS <= 59039 44  59039 < BS <= 72598 45  72598 < BS <=89272 46  89272 < BS <= 109774 47  109774 < BS <= 134986 48  134986 < BS<= 165989 49  165989 < BS <= 204111 50  204111 < BS <= 250990 51  250990< BS <= 308634 52  308634 < BS <= 379519 53  379519 < BS <= 466683 54 466683 < BS <= 573866 55  573866 < BS <= 705666 56  705666 < BS <=867737 57  867737 < BS <= 1067031 58 1067031 < BS <= 1312097 59 1312097< BS <= 1613447 60 1613447 < BS <= 1984009 61 1984009 < BS <= 2439678 622439678 < BS <= 3000000 63 BS > 3000000

FIG. 9 is an example of default data path for communication between twoUEs. With reference to FIG. 9, even when two UEs (e.g., UE1, UE2) inclose proximity communicate with each other, their data path (userplane) goes via the operator network. Thus a typical data path for thecommunication involves eNB(s) and/or Gateway(s) (GW(s)) (e.g., SGW/PGW).

FIGS. 10 and 11 are examples of data path scenarios for a proximitycommunication. If wireless devices (e.g., UE1, UE2) are in proximity ofeach other, they may be able to use a direct mode data path (FIG. 10) ora locally routed data path (FIG. 11). In the direct mode data path,wireless devices are connected directly each other (after appropriateprocedure(s), such as authentication), without eNB and SGW/PGW. In thelocally routed data path, wireless devices are connected each otherthrough eNB only.

FIG. 12 is a conceptual diagram illustrating for a non-roaming referencearchitecture.

PC1 to PC5 represent interfaces. PC1 is a reference point between aProSe application in a UE and a ProSe App server. It is used to defineapplication level signaling requirements. PC2 is a reference pointbetween the ProSe App Server and the ProSe Function. It is used todefine the interaction between ProSe App Server and ProSe functionalityprovided by the 3GPP EPS via ProSe Function. One example may be forapplication data updates for a ProSe database in the ProSe Function.Another example may be data for use by ProSe App Server in interworkingbetween 3GPP functionality and application data, e.g. name translation.PC3 is a reference point between the UE and ProSe Function. It is usedto define the interaction between UE and ProSe Function. An example maybe to use for configuration for ProSe discovery and communication. PC4is a reference point between the EPC and ProSe Function. It is used todefine the interaction between EPC and ProSe Function. Possible usecases may be when setting up a one-to-one communication path between UEsor when validating ProSe services (authorization) for session managementor mobility management in real time.

PC5 is a reference point between UE to UE used for control and userplane for discovery and communication, for relay and one-to-onecommunication (between UEs directly and between UEs over LTE-Uu).Lastly, PC6 is a reference point may be used for functions such as ProSeDiscovery between users subscribed to different PLMNs.

Especially, the following identities are used for ProSe DirectCommunication:

-   -   Source Layer-2 ID identifies a sender of a D2D packet at PC5        interface. The Source Layer-2 ID is used for identification of        the receiver RLC UM entity;    -   Destination Layer-2 ID identifies a target of the D2D packet at        PC5 interface. The Destination Layer-2 ID is used for filtering        of packets at the MAC layer. The Destination Layer-2 ID may be a        broadcast, groupcast or unicast identifier; and    -   SA L1 ID identifier in Scheduling Assignment (SA) at PC5        interface. SA L1 ID is used for filtering of packets at the        physical layer. The SA L1 ID may be a broadcast, groupcast or        unicast identifier.

No Access Stratum signaling is required for group formation and toconfigure Source Layer-2 ID and Destination Layer-2 ID in the UE. Thisinformation is provided by higher layers.

In case of groupcast and unicast, the MAC layer will convert the higherlayer ProSe ID (i.e. ProSe Layer-2 Group ID and ProSe UE ID) identifyingthe target (Group, UE) into two bit strings of which one can beforwarded to the physical layer and used as SA L1 ID whereas the otheris used as Destination Layer-2 ID. For broadcast, L2 indicates to L1that it is a broadcast transmission using a pre-defined SA L1 ID in thesame format as for group- and unicast.

In summary, for the PC5 interface, there are several features asfollowing:

i) The Source Layer-2 ID and the Destination Layer-2 ID in front of theMAC PDU without MAC subheader, ii) It is too early to exclude MAC CE forD2D, iii) One D2D group can be composed of UEs supporting different MACPDU formats, iv) Include a MAC PDU format version number in the firstfield of D2D MAC PDU, v) Separate HARQ entity for D2D.

On the other hand, for the Uu interface, there are several featuresdifferent from the PC5 interface as following:

i) It might be beneficial for the network to know which buffer statusinformation is mapped to which D2D communication groups of a UE, ii)Group Index is informed to the eNB by BSR (either explicit or implicit),iii) The eNB is aware of Group ID, and mapping relation between Group IDand Group Index, and iv) The UE reports Group ID, and mapping relationbetween Group ID and Group Index to the eNB.

FIG. 13A is a conceptual diagram illustrating for User-Plane protocolstack for ProSe Direct Communication, and FIG. 13B is Control-Planeprotocol stack for ProSe Direct Communication.

FIG. 13A shows the protocol stack for the user plane, where PDCP, RLCand MAC sublayers (terminate at the other UE) perform the functionslisted for the user plane (e.g. header compression, HARQretransmissions). The PC5 interface consists of PDCP, RLC, MAC and PHYas shown in FIG. 13A.

User plane details of ProSe Direct Communication: i) There is no HARQfeedback for ProSe Direct Communication, ii) MAC sub header containsLCIDs (to differentiate multiple logical channels), iii) The MAC headercomprises a Source Layer-2 ID and a Destination Layer-2 ID, iv) At MACMultiplexing/demultiplexing, priority handling and padding are usefulfor ProSe Direct communication, v) RLC UM is used for ProSe Directcommunication, vi) Segmentation and reassembly of RLC SDUs areperformed, vii) A receiving UE needs to maintain at least one RLC UMentity per transmitting peer UE, viii) An RLC UM receiver entity doesnot need to be configured prior to reception of the first RLC UM dataunit, and ix) U-Mode is used for header compression in PDCP for ProSeDirect Communication.

A UE may establish multiple logical channels. LCID included within theMAC subheader uniquely identifies a logical channel within the scope ofone source Layer-2 ID and Destination Layer-2 ID combination. Alllogical channels are mapped to one specified logical channel group (e.g.LCGID 3). It is up to the UE implementation in which order to serve thelogical channels. Parameters for Logical channel prioritization are notconfigured

FIG. 13B shows the protocol stack for the control plane, where RRC, RLC,MAC, and PHY sublayers (terminate at the other UE) perform the functionslisted for the control plane. A D2D UE does not establish and maintain alogical connection to receiving D2D UEs prior to a ProSe Directcommunication.

FIG. 14 is a conceptual diagram illustrating for a PC5 interface fordevice to device direct discovery.

ProSe Direct Discovery is defined as the procedure used by theProSe-enabled UE to discover other ProSe-enabled UE(s) in its proximityusing E-UTRA direct radio signals via PC5. ProSe Direct Discovery issupported only when the UE is served by E-UTRAN.

Upper layer handles authorization for announcement and monitoring ofdiscovery information. Content of discovery information is transparentto Access Stratum (AS) and no distinction in AS is made for ProSe DirectDiscovery models and types of ProSe Direct Discovery.

The UE can participate in announcing and monitoring of discoveryinformation in both RRC IDLE and RRC CONNECTED state as per eNBconfiguration. The UE announces and monitors its discovery informationsubject to the half-duplex constraint.

Announcing and Monitoring UE maintains the current UTC time. AnnouncingUE transmits the discovery message which is generated by the ProSeprotocol taking into account the UTC time upon transmission of thediscovery message. In the monitoring UE the ProSe protocol provides themessage to be verified together with the UTC time upon reception of themessage to the ProSe function.

The Radio Protocol Stack (AS) for ProSe Direct Discovery consists ofonly MAC and PHY.

The AS layer performs the following functions:

-   -   Interfaces with upper layer (ProSe Protocol): The MAC layer        receives the discovery information from the upper layer (ProSe        Protocol). The IP layer is not used for transmitting the        discovery information.    -   Scheduling: The MAC layer determines the radio resource to be        used for announcing the discovery information received from        upper layer.    -   Discovery PDU generation: The MAC layer builds the MAC PDU        carrying the discovery information and sends the MAC PDU to the        physical layer for transmission in the determined radio        resource. No MAC header is added.

There are two types of resource allocation for discovery informationannouncement.

-   -   Type 1: A resource allocation procedure where resources for        announcing of discovery information are allocated on a non UE        specific basis, further characterized by: i) The eNB provides        the UE(s) with the resource pool configuration used for        announcing of discovery information. The configuration may be        signaled in SIB, ii) The UE autonomously selects radio        resource(s) from the indicated resource pool and announce        discovery information, iii) The UE can announce discovery        information on a randomly selected discovery resource during        each discovery period.    -   Type 2: A resource allocation procedure where resources for        announcing of discovery information are allocated on a per UE        specific basis, further characterized by: i) The UE in RRC        CONNECTED may request resource(s) for announcing of discovery        information from the eNB via RRC, ii) The eNB assigns        resource(s) via RRC, iii) The resources are allocated within the        resource pool that is configured in UEs for monitoring.

For UEs in RRC IDLE, the eNB may select one of the following options:

-   -   The eNB may provide a Type 1 resource pool for discovery        information announcement in SIB. UEs that are authorized for        Prose Direct Discovery use these resources for announcing        discovery information in RRC IDLE.    -   The eNB may indicate in SIB that it supports D2D but does not        provide resources for discovery information announcement. UEs        need to enter RRC Connected in order to request D2D resources        for discovery information announcement.

For UEs in RRC_CONNECTED,

-   -   A UE authorized to perform ProSe Direct Discovery announcement        indicates to the eNB that it wants to perform D2D discovery        announcement.    -   The eNB validates whether the UE is authorized for ProSe Direct        Discovery announcement using the UE context received from MME.    -   The eNB may configure the UE to use a Type 1 resource pool or        dedicated Type 2 resources for discovery information        announcement via dedicated RRC signaling (or no resource).    -   The resources allocated by the eNB are valid until a) the eNB        de-configures the resource(s) by RRC signaling or b) the UE        enters IDLE. (FFS whether resources may remain valid even in        IDLE).

Receiving UEs in RRC_IDLE and RRC_CONNECTED monitor both Type 1 and Type2 discovery resource pools as authorized. The eNB provides the resourcepool configuration used for discovery information monitoring in SIB. TheSIB may contain discovery resources used for announcing in neighborcells as well.

By supporting ProSe communication, the data are transmitted over eitherPC5 interface or Uu interface. Although there is no explicit agreementon having a separate ProSe BSR for ProSe communication, it seems to be acommon RAN2 understanding that the UE uses ProSe BSR for requestingresource for the data transmission over PC5 interface.

FIG. 15 is a conceptual diagram for priority handling buffer statusreporting according to embodiments of the present invention.

It was pointed out that priority handling rule is needed for ProSe BSR.In this application, we discuss how the UE handles ProSe BSR MAC CE inLCP procedure.

In MAC specification, for LCP procedure, the relative priority isdefined as follows,

-   -   MAC control element for C-RNT1 or data from UL-CCCH;    -   MAC control element for BSR, with exception of BSR included for        padding;    -   MAC control element for PHR or Extended PHR;    -   data from any Logical Channel, except data from UL-CCCH;    -   MAC control element for BSR included for padding.

As ProSe BSR is newly introduced for Prose communication, RAN2 need todefine the relative priority for ‘MAC CE for ProSe BSR, with exceptionof ProSe BSR included for padding’ and ‘MAC CE for ProSe BSR includedfor padding’.

In general, the legacy operation shouldn't be impeded by the additionalfeature unless it is justified in terms of motivation/gain/complexity.In this sense, ‘MAC CE for ProSe BSR, with exception of ProSe BSRincluded for padding’ has to have lower priority than at least ‘MACcontrol element for BSR, with exception of BSR included for padding’.

Padding BSR is additional information which could be transmitted onlywhen uplink resource is left to include Padding BSR. As ProSecommunication is additional feature in Rel-12, it is straightforwardthat ‘MAC CE for ProSe BSR included for padding’ has the lowest priorityin LCP procedure, i.e., lower priority than ‘MAC CE for BSR included forpadding’.

Then, there are three options as follows:

1. Option 1 is to prioritize the MAC CE for ProSe BSR over the MAC CEfor PHR. Although PHR MAC CE is deprioritized than BSR MAC CE in legacyoperation, it doesn't mean that PHR MAC CE has lower priority than ProSeBSR MAC CE as well. Considering that PHR MAC CE carries importantscheduling assistant information for data transmission over Uuinterface, Option 1 seems not desirable as it possibly has a negativeimpact on scheduling for Uu interface as well as data transmission on Uuinterface.

Regarding the option 1, the relative priority is defined as follows:

i) MAC control element for C-RNTI or data from UL-CCCH;

ii) MAC control element for BSR, with exception of BSR included forpadding;

iii) MAC control element for ProSe BSR, with exception of ProSe BSRincluded for padding;

iv) MAC control element for PHR or Extended PHR;

v) Data from any Logical Channel, except data from UL-CCCH;

vi) MAC control element for BSR included for padding; and

vii) MAC CE for ProSe BSR included for padding.

2. Option 2 is to prioritize ‘scheduling assistant information for datatransmission over Uu interface’ over ‘scheduling assistant informationfor data transmission over PC5 interface’. In option 2, datatransmission over Uu interface is deprioritized than the MAC CE forProSe BSR, hence, it also has an impact on data transmission on Uuinterface. However, Option 2 is acceptable because delayed datatransmission might not be a critical problem.

Regarding the option 2, the relative priority is defined as follows:

i) MAC control element for C-RNTI or data from UL-CCCH;

ii) MAC control element for BSR, with exception of BSR included forpadding;

iii) MAC control element for PHR or Extended PHR;

iv) MAC control element for ProSe BSR, with exception of ProSe BSRincluded for padding;

v) Data from any Logical Channel, except data from UL-CCCH;

vi) MAC control element for BSR included for padding; and

vii) MAC CE for ProSe BSR included for padding.

3. Option 3 is to prioritize ‘data transmission over Uu interface andscheduling assistant information for Uu interface’ over ‘datatransmission over PC5 interface and scheduling assistant information forPC5 interface’. In Option 3, if there is continuous on-going uplink datatransmission over Uu interface, the ProSe BSR would be delayed for along time. Considering that ProSe BSR MAC CE carries importantscheduling assistant information for PC5 interface, Option 3 is notacceptable.

Regarding the option 3, the relative priority is defined as follows:

i) MAC control element for C-RNTI or data from UL-CCCH;

ii) MAC control element for BSR, with exception of BSR included forpadding;

iii) MAC control element for PHR or Extended PHR;

iv) Data from any Logical Channel, except data from UL-CCCH;

v) MAC control element for ProSe BSR, with exception of ProSe BSRincluded for padding;

vi) MAC control element for BSR included for padding; and

vii) MAC CE for ProSe BSR included for padding.

With above analysis, Option 2 is preferred because it has an acceptableimpact on data transmission over Uu interface while enabling ProSecommunication. Thus, our invention refers that ‘MAC CE for ProSe BSR,with exception of BSR included for padding’ has higher priority than Uudata but has lower priority than Uu scheduling assistant information,i.e., Option 2.

Regarding FIG. 15, when the UE generates a MAC PDU if both of a PHR(Power Headroom Reporting) and a sidelink BSR (Buffer Status Reporting)are generated while the UE communicates with other UEs directly using asidelink,

the PHR is prioritized over the sidelink BSR when the UE prioritizesbetween the PHR and the sidelink BSR in the generated MAC PDU (S1501).

Preferably, the PHR is related to scheduling assistant information foruplink data transmission via Uu interface.

Preferably, the PHR is transmitted using a PHR MAC CE, an extended PHRMAC CE, or a dual connectivity PHR MAC CE.

The UE allocates an uplink resource to a PHR MAC CE and a correspondingMAC sub-header in the MAC PDU (S1503), and then checks whether aremaining uplink resource in the MAC PDU can accommodate a sidelink BSRMAC CE and a corresponding MAC sub-header (S1505).

If the remaining uplink resource can accommodate the sidelink BSR MAC CEand the corresponding MAC sub-header, the UE can allocate an uplinkresource to the sidelink BSR MAC CE and the corresponding MAC sub-header(S1507). If there is no remaining uplink resource after the UE allocatesan uplink resource to a PHR MAC CE and a corresponding MAC sub-header inthe MAC PDU, the UE cannot allocate an uplink resource to the sidelinkBSR MAC CE and the corresponding MAC sub-header (S1509).

After the UE allocates the uplink resource to the sidelink BSR MAC CEand the corresponding MAC sub-header in the MAC PDU, the UE allocates aremaining uplink resource in MAC PDU to uplink data except data fromUL-CCCH, or padding BSR (S1511).

The UE transmits the MAC PDU after generating the MAC PDU (S1513).

FIG. 16 is an example for priority handling buffer status reportingaccording to embodiments of the present invention.

The UE triggers a Regular BSR for Uu data and a Regular BSR for PC5 datasimultaneously. Regarding Uu BSR, the UE reports a long BSR becausethere are multiple LCG that has data available for transmission. The UEhas total 100 bytes of Uu data available for transmission, which is notfrom UL-CCCH.

Regarding ProSe BSR, the UE report a BS for the Group of which the databecomes available for transmission.

The UE is allocated with 60 bytes of uplink resource. When the UE hasuplink resource allocated for new transmission for this TTI, the UEgenerates the Uu BSR MAC CE, firstly. The size of Uu BSR MAC CE is 3bytes. And then, the UE generates the ProSe BSR MAC CE. The size ofProSe BSR MAC CE is, e.g., 1 byte.

In the 60 bytes of MAC PDU, the UE allocates uplink resource to Uu BSRMAC CE and the corresponding MAC sub-header, which consumes 4 bytes. Theremaining space in MAC PDU is 56 bytes.

The UE checks if the remaining space in MAC PDU can allocate uplinkresource to the ProSe BSR MAC CE and the corresponding MAC sub-header.If yes, the UE allocate uplink resource to ProSe BSR MAC CE and thecorresponding MAC sub-header, which consumes 2 bytes. The remainingspace in MAC PDU is 54 bytes.

In the remaining 54 bytes of MAC PDU, the UE allocate uplink resource toMAC SDUs for Uu data and the corresponding MAC sub-headers, whichconsumes rest of the allocated uplink resource, i.e., 54 bytes.

As an example, the generated MAC PDU is shown in the FIG. 16. As long asthe MAC CEs are placed before the MAC SDUs and after the MAC header,there is no specific placing order between MAC CEs.

The embodiments of the present invention described herein below arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It is obvious tothose skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim bysubsequent amendment after the application is filed.

In the embodiments of the present invention, a specific operationdescribed as performed by the BS may be performed by an upper node ofthe BS. Namely, it is apparent that, in a network comprised of aplurality of network nodes including a BS, various operations performedfor communication with an MS may be performed by the BS, or networknodes other than the BS. The term ‘eNB’ may be replaced with the term‘fixed station’, ‘Node B’, ‘Base Station (BS)’, ‘access point’, etc.

The above-described embodiments may be implemented by various means, forexample, by hardware, firmware, software, or a combination thereof

In a hardware configuration, the method according to the embodiments ofthe present invention may be implemented by one or more ApplicationSpecific Integrated Circuits (ASICs), Digital Signal Processors (DSPs),Digital Signal Processing Devices (DSPDs), Programmable Logic Devices(PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers,microcontrollers, or microprocessors.

In a firmware or software configuration, the method according to theembodiments of the present invention may be implemented in the form ofmodules, procedures, functions, etc. performing the above-describedfunctions or operations. Software code may be stored in a memory unitand executed by a processor. The memory unit may be located at theinterior or exterior of the processor and may transmit and receive datato and from the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

What is claimed is:
 1. A method for transmitting, by a user equipment(UE), data in a wireless communication system, the method comprising:generating, at the UE, a medium access control (MAC) protocol data unit(PDU) containing at least one of a power headroom report (PHR) and asidelink buffer status report (BSR); and transmitting, by the UE, theMAC PDU using uplink (UL) resources allocated to the UE, wherein the UEgenerates the MAC PDU, based on the UL resources and a predefinedrelative priority of a logical channel prioritization procedure, andwherein the predefined relative priority includes a following relativepriority in decreasing order: MAC control element for PHR; and MACcontrol element for sidelink BSR.
 2. The method according to claim 1,wherein the predefined relative priority includes a following relativepriority in decreasing order: MAC control element for PHR or extendedPHR; MAC control element for sidelink BSR, with exception of sidelinkBSR included for padding; and data from any logical channel, except datafrom UL common control channel (UL-CCCH).
 3. The method according toclaim 1, wherein the predefined relative priority includes a followingrelative priority in decreasing order: MAC control element for C-RNTI ordata from UL-CCCH; MAC control element for BSR, with exception of BSRincluded for padding; MAC control element for PHR or extended PHR; MACcontrol element for sidelink BSR, with exception of sidelink BSRincluded for padding; data from any logical channel, except data from ULcommon control channel (UL-CCCH); MAC control element for BSR includedfor padding; and MAC control element for sidelink BSR included forpadding.
 4. The method according to claim 1, wherein the sidelink BSR isnot a sidelink BSR included for padding; wherein the UE generates theMAC PDU to contain both the PHR and the sidelink BSR if remaining ULresources after the UE allocates an uplink resource to a MAC controlelement (PHR MAC CE) containing the PHR and a MAC sub-header for the PHRMAC CE can accommodate a MAC control element (sidelink BSR MAC CE)containing the sidelink BSR and a MAC sub-header for the sidelink BSRMAC CE; and wherein the UE generates the MAC PDU to contain the PHR andnot to contain the sidelink BSR if the remaining UL resource cannotaccommodate the sidelink BSR MAC CE and the MAC sub-header for thesidelink BSR MAC CE.
 5. The method according to claim 1, wherein the PHRis related to scheduling assistant information for uplink datatransmission via a Uu interface.
 6. The method according to claim 1,wherein the sidelink BSR includes information about an amount ofsidelink data available for transmission over an PC5 interface.
 7. Auser equipment (UE) for transmitting data in a wireless communicationsystem, the UE comprising: a radio frequency (RF) module; and aprocessor configured to control the RF module, the processor configuredto: generate a medium access control (MAC) protocol data unit (PDU)containing at least one of a power headroom report (PHR) and a sidelinkbuffer status report (BSR); and control the RF unit to transmit the MACPDU using uplink (UL) resources allocated to the UE, wherein theprocessor is configured to generate the MAC PDU, based on the ULresources and a predefined relative priority of a logical channelprioritization procedure, and wherein the predefined relative priorityincludes a following relative priority in decreasing order: MAC controlelement for PHR; and MAC control element for sidelink BSR.
 8. The UEaccording to claim 7, wherein the predefined relative priority includesa following relative priority in decreasing order: MAC control elementfor PHR or extended PHR; MAC control element for sidelink BSR, withexception of sidelink BSR included for padding; and data from anylogical channel, except data from UL common control channel (UL-CCCH).9. The UE according to claim 7, wherein the predefined relative priorityincludes a following relative priority in decreasing order: MAC controlelement for C-RNTI or data from UL-CCCH; MAC control element for BSR,with exception of BSR included for padding; MAC control element for PHRor extended PHR; MAC control element for sidelink BSR, with exception ofsidelink BSR included for padding; data from any logical channel, exceptdata from UL common control channel (UL-CCCH); MAC control element forBSR included for padding; and MAC control element for sidelink BSRincluded for padding.
 10. The UE according to claim 1, wherein thesidelink BSR is not a sidelink BSR included for padding; wherein theprocessor is configured to generate the MAC PDU to contain both the PHRand the sidelink BSR if remaining UL resources after allocating anuplink resource to a MAC control element (PHR MAC CE) containing the PHRand a MAC sub-header for the PHR MAC CE can accommodate a MAC controlelement (sidelink BSR MAC CE) containing the sidelink BSR and a MACsub-header for the sidelink BSR MAC CE; and wherein the processor isconfigured to generate the MAC PDU to contain the PHR and not to containthe sidelink BSR if the remaining UL resource cannot accommodate thesidelink BSR MAC CE and the MAC sub-header for the sidelink BSR MAC CE.11. The UE according to claim 7, wherein the PHR is related toscheduling assistant information for uplink data transmission via a Uuinterface.
 12. The UE according to claim 7, wherein the sidelink BSRincludes information about an amount of sidelink data available fortransmission over an PC5 interface.